why dart not supports multiple inheritance

void main(List<String> arguments) {}

// code becomes very complex or to understand in Multiple heritance

class MyLogin extends AuthClass with MyRewards, Authentication, Authentication {
  @override
  logout() {
    throw UnimplementedError();
  }
}

abstract class AuthClass {
  logout();
}

mixin MyRewards {
  int points = 100;
}

/**
 * User
 * Admin
 * Moderator
 */

class User with Authentication {}

class Admin with Authentication {}

class Moderator with Authentication {}

mixin Authentication {
  int cibiliPoints = 0;
  bool isLogin = false;
  setLogin(bool status) {
    isLogin = status;
  }

  logout() {
    // logout
  }

  getCibilPoints() {}

  bool isHeElgible() {
    if (cibiliPoints > 730) {
      return true;
    } else {
      return false;
    }
  }
}



/**
 * In Dart, a mixin is a way to reuse a class's code in multiple class hierarchies.
 * A mixin is defined like a regular class,
 * but it is intended to be used as a component of a class rather than a standalone class.
 * To use a mixin, a class includes it using the "with" keyword.
 * This allows the class that uses the mixin to have access to the mixin's methods and fields,
 * as if they were defined in the class itself.
 */